drivers: eeprom: at2x: remove '&' when assigning `init_fn`

To maintain consistency in `init_fn` parameter passing,
remove the address-of operator ('&') when assigning the `init_fn`
function pointer in the `DEVICE_DT_INST_DEFINE` macro.

Signed-off-by: Pisit Sawangvonganan <pisit@ndrsolution.com>